// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/i18n/case_conversion.h"

#include <stdint.h>

#include "base/numerics/safe_conversions.h"
#include "base/strings/string16.h"
#include "base/strings/string_util.h"
#include "third_party/icu/source/common/unicode/uchar.h"
#include "third_party/icu/source/common/unicode/unistr.h"
#include "third_party/icu/source/common/unicode/ustring.h"

namespace base {
namespace i18n {

    namespace {

        // Provides a uniform interface for upper/lower/folding which take take
        // slightly varying parameters.
        typedef int32_t (*CaseMapperFunction)(UChar* dest, int32_t dest_capacity,
            const UChar* src, int32_t src_length,
            UErrorCode* error);

        int32_t ToUpperMapper(UChar* dest, int32_t dest_capacity,
            const UChar* src, int32_t src_length,
            UErrorCode* error)
        {
            // Use default locale.
            return u_strToUpper(dest, dest_capacity, src, src_length, NULL, error);
        }

        int32_t ToLowerMapper(UChar* dest, int32_t dest_capacity,
            const UChar* src, int32_t src_length,
            UErrorCode* error)
        {
            // Use default locale.
            return u_strToLower(dest, dest_capacity, src, src_length, NULL, error);
        }

        int32_t FoldCaseMapper(UChar* dest, int32_t dest_capacity,
            const UChar* src, int32_t src_length,
            UErrorCode* error)
        {
            return u_strFoldCase(dest, dest_capacity, src, src_length,
                U_FOLD_CASE_DEFAULT, error);
        }

        // Provides similar functionality as UnicodeString::caseMap but on string16.
        string16 CaseMap(StringPiece16 string, CaseMapperFunction case_mapper)
        {
            string16 dest;
            if (string.empty())
                return dest;

            // Provide an initial guess that the string length won't change. The typical
            // strings we use will very rarely change length in this process, so don't
            // optimize for that case.
            dest.resize(string.size());

            UErrorCode error;
            do {
                error = U_ZERO_ERROR;

                // ICU won't terminate the string if there's not enough room for the null
                // terminator, but will otherwise. So we don't need to save room for that.
                // Don't use WriteInto, which assumes null terminators.
                int32_t new_length = case_mapper(
                    &dest[0], saturated_cast<int32_t>(dest.size()),
                    string.data(), saturated_cast<int32_t>(string.size()),
                    &error);
                dest.resize(new_length);
            } while (error == U_BUFFER_OVERFLOW_ERROR);
            return dest;
        }

    } // namespace

    string16 ToLower(StringPiece16 string)
    {
        return CaseMap(string, &ToLowerMapper);
    }

    string16 ToUpper(StringPiece16 string)
    {
        return CaseMap(string, &ToUpperMapper);
    }

    string16 FoldCase(StringPiece16 string)
    {
        return CaseMap(string, &FoldCaseMapper);
    }

} // namespace i18n
} // namespace base
